CN114276042B - Alkali-free fluorine-free liquid accelerator and preparation method thereof - Google Patents
Alkali-free fluorine-free liquid accelerator and preparation method thereof Download PDFInfo
- Publication number
- CN114276042B CN114276042B CN202111628630.XA CN202111628630A CN114276042B CN 114276042 B CN114276042 B CN 114276042B CN 202111628630 A CN202111628630 A CN 202111628630A CN 114276042 B CN114276042 B CN 114276042B
- Authority
- CN
- China
- Prior art keywords
- accelerator
- free
- stirring
- alkali
- liquid accelerator
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Active
Links
Classifications
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
- Y02W30/00—Technologies for solid waste management
- Y02W30/50—Reuse, recycling or recovery technologies
- Y02W30/91—Use of waste materials as fillers for mortars or concrete
Landscapes
- Curing Cements, Concrete, And Artificial Stone (AREA)
Abstract
The invention belongs to the technical field of concrete admixtures, and particularly relates to an alkali-free fluorine-free liquid accelerator and a preparation method thereof; the accelerator is an alkali-free fluorine-free environment-friendly liquid accelerator formed by matching mother liquor of four components of polyaluminium sulfate, magnesium sulfate, diethanolamine and ethylene glycol with modified silicon dioxide, a defoaming agent and a dispersing agent, and the preferable proportion of the accelerator is 53-57% of polyaluminium sulfate and 4-6% of diethanolamine; 2-3% of magnesium sulfate; 1-2% of ethylene glycol; 2-4% of modified silicon dioxide, 0.2-1.5% of defoaming agent and 2-6% of dispersing agent; the balance is made up to 100 percent by water. The accelerator is green, environment-friendly and pollution-free, is simple to prepare, has high early strength of concrete, small loss of later strength, good stability and adaptability, economy, environmental protection and other performances.
Description
Technical Field
The invention belongs to the technical field of concrete admixtures, and particularly relates to an alkali-free fluorine-free liquid accelerator and a preparation method thereof.
Background
In tunnel construction, it is a common method to reinforce surrounding rocks with shotcrete. The shotcrete can be classified into a wet spraying method or a dry spraying method according to construction methods. With the improvement of the requirements of China on the quality of sprayed concrete and the operation environment, the dry spraying concrete technology is inevitably eliminated by the wet spraying concrete technology in the future, so the demand for high-quality liquid setting accelerators is increased more and more.
The liquid accelerator is mostly alkaline accelerator, and the traditional alkaline liquid accelerator is prepared by taking water glass (silicate) as a main component and adding potassium dichromate, triethanolamine and the like. The alkali content of the accelerator reaches 25%, the corrosion is extremely strong, and meanwhile, the accelerator has extremely high loss on the later strength of concrete and is expensive. The low-alkali liquid accelerator with sodium (potassium) aluminate and an organic reinforcing agent as main components can reduce the alkali content to 10-20%, researchers carry out modification research on the low-alkali liquid accelerator in order to lower the alkali content, and common modifiers comprise aluminum sulfate, sodium fluoride and the like.
However, the alkaline liquid accelerator always cannot avoid a series of problems caused by the introduction of alkali metal. The problems caused by alkali metals are mainly the following three: firstly, higher alkali content will cause loss of later strength of mortar concrete. Secondly, the introduced alkali is easy to cause alkali aggregate reaction, so that the concrete is easy to generate the bad phenomenon of expansion and damage, and the long-term durability of the concrete is adversely affected. Thirdly, the alkaline accelerating agent has strong corrosivity, is easy to damage the respiratory system, eyes and other important organs of construction workers, and has great harm to human bodies.
In addition, in the selection of the raw material of the liquid accelerator, a large amount of fluorine-containing compounds such as hydrofluoric acid, sodium fluoride, magnesium fluorosilicate, magnesium aluminum fluoride and the like are used in large amounts. However, the existence of fluoride can cause the early strength of concrete to develop slowly, the harm of the fluorine-containing accelerator to human bodies and the environment in the production and application processes is not small, the fluorine storage in human bodies is high, poisoning is caused, the fluorine spot is caused when the fluorine storage in human bodies is high, and the fluorine bone cancer is caused when the fluorine storage in human bodies is high.
The main problems of the development and application of the current alkali-free (low-alkali) liquid accelerator are still the contradiction between accelerating efficiency, storage stability and adaptability.
Disclosure of Invention
The invention aims to: aiming at the technical defects of poor accelerating effect, large mixing amount and low stability of the alkali-free/low-alkali liquid accelerator in the prior art, the novel alkali-free fluorine-free liquid accelerator with good stability and high strength retention rate and the preparation method thereof are provided by researching the aspects of the design of components of the alkali-free fluorine-free liquid accelerator, the synthesis preparation of the liquid accelerator, the stability and adaptability control of the alkali-free fluorine-free liquid accelerator, the accelerating control of the liquid accelerator, the engineering application technology of the alkali-free fluorine-free liquid accelerator and the like from the optimization of the components of the alkali-free fluorine-free liquid accelerator.
In order to achieve the purpose, the invention adopts the technical scheme that:
an alkali-free fluorine-free liquid accelerator comprises the following raw materials in percentage by mass:
50-60% of polyaluminum sulfate, 4-8% of diethanolamine, 1-5% of magnesium sulfate, 1-4% of ethylene glycol, 2-5% of modifier and the balance of water to 100%;
the modifier is modified silicon dioxide; the modified silicon dioxide is obtained by using nano silicon dioxide as a matrix and adopting a silane coupling agent to carry out polymerization with the nano silicon dioxide.
It is well known to those skilled in the art that increasing the necessary alkali content can accelerate the setting hydration of concrete, meeting the initial setting time and final setting time specifications. When alkali is not introduced, the requirement on how to ensure the setting time of the cement paste is a technical difficulty; and hydrofluoric acid or other fluorides can effectively improve the solubility of aluminum ions, thereby achieving the effects of accelerating coagulation and stable storage. The stabilizing agent is selected to replace fluoride, so that the accelerating effect of the liquid accelerator can be ensured, and the long-term stable storage of the accelerator can be realized; the invention makes stricter technical requirements on the alkali content of the liquid accelerator, and particularly provides a compound composition, wherein polyaluminium sulfate is taken as a main accelerator, diethanolamine and ethylene glycol are taken as complexing agents, magnesium sulfate and modified silicon dioxide are matched to be taken as an early strength agent, and the alkali-free fluorine-free liquid accelerator with better accelerating effect is obtained by compounding the polyaluminium sulfate as the main accelerator, the diethanolamine and the ethylene glycol according to a certain proportion; the cement setting time is obviously shortened, and the stability of the accelerator is ensured to be at a higher level. The method has the characteristics of no demixing and no precipitation, and good compressive strength for a long time; and has good adaptability to various cement products on the market.
As the main quick-setting component, the aluminum ions in the aluminum sulfate can be hydrated with Ca (OH) generated by cement 2 The reaction generates hydrated calcium aluminate, hydrated calcium sulphoaluminate and other products, so that the cement slurry is coagulated. Therefore, to satisfy the requirement of rapid setting of cement, al must be increased 2 (SO 4 ) 3 The amount of the solution is such that a sufficient aluminum ion content is achieved in the cement hydration environment, but Al is present 2 (SO 4 ) 3 Too high a quantity of solution may adversely affect the stability of the accelerator, al 2 (SO 4 ) 3 The larger the dosage, the worse the accelerator stability; preferably, the ratio of the polyaluminium sulfate to the accelerator is 53-57%;
the preparation method of the alkali-free and fluorine-free liquid accelerator mainly takes alcohol amine as a main dissolution promoting component to promote the dissolution of aluminum sulfate, and improves the interaction state of particles in the liquid accelerator by utilizing a complex reaction to achieve the effect of accelerating the accelerator. The inventor discovers that the stability is improved by carrying out mixing amount experiments on diethanol amine in different proportions; however, as the amount of the diethanolamine-containing admixture is increased, the later strength of the mortar is not reduced, but the early strength is extremely disadvantageous, and therefore, the amount of the diethanolamine needs to be balanced and controlled within a proper range.
Like diethanolamine, ethylene glycol is mainly used as a dissolution promoting component to promote the dissolution of aluminum sulfate, and the concentration of aluminum sulfate in an aqueous solution is increased, and in the process of researching the mixing amount of ethylene glycol mono-component: with the increase of the mixing amount of the ethylene glycol, the setting time and stability curve of the cement paste shows the trend of firstly reducing and then prolonging, when the mixing amount of the ethylene glycol is 2 percent, the alkali-free fluorine-free liquid accelerator has the best action effect, but the setting time can not reach the standard of qualified products of national standard quick-setting agents.
In order to make up for the defects of the two materials, namely diethanolamine and ethylene glycol, the invention discovers through experimental research that: the two materials are synergistic, and the setting time of the setting accelerator can be effectively shortened by adjusting the proportion of the two materials. The stability of the accelerator is improved by the cooperation and synergy of diethanolamine and ethylene glycol, and as a preferable scheme of the invention, the ratio of the diethanolamine to the ethylene glycol is (4-8): 1; preferably, the mixing amount of the diethanol amine accounts for 4-5% of the ratio of the accelerating agent.
Through further research on the performance of cement by different incorporation amounts of magnesium sulfate in a quick-dissolving agent, the addition of the magnesium sulfate can accelerate C 3 And the hydration of S ensures that the cement obtains higher early strength. Preferably, the optimal mixing amount of the magnesium sulfate heptahydrate ranges from 2% to 2.5% of the total amount of the accelerating agent.
More preferably, the accelerator comprises the following raw materials in parts by weight:
53-57% of polyaluminium sulfate, 4-6% of diethanolamine, 2-3% of magnesium sulfate and 1-2% of ethylene glycol.
In the process of researching the compound composition, the inventor discovers the optimal proportion of the liquid accelerator by a large amount of optimization experiments, and researches, compounding and optimization are respectively carried out on indexes such as initial setting time, final setting time, 1d compressive strength, 28-day compressive strength and the like when the mother liquor prepared by 4 components of polyaluminium sulfate, diethanol amine, magnesium sulfate and ethylene glycol and water is subjected to measurement such as cement paste setting time, cement mortar compressive strength and the like according to the mixing amount of 7%. Through trying a plurality of modifiers to carry out different mixing amount experiments, the nano silicon dioxide has an obvious effect on improving the early strength of the mortar, preferably, the mixing amount of the nano silicon dioxide in mother liquor is 2% -3%, the nano silicon dioxide has a strong hydration characteristic under an alkaline condition, and meanwhile, a small particle size can play a good filling role, so that the mortar and concrete structures become more compact.
As a preferred embodiment of the present invention, the modifier is modified specifically as follows:
modifying nano silicon dioxide by using a silane coupling agent with the nano silicon dioxide as a matrix, adding dilute sulfuric acid to promote hydroxyl in the silane coupling agent to generate a polymerization reaction with the silicon dioxide, and placing the reacted solution in an ultrasonic dispersion instrument for 3-5min to obtain the modified nano silicon dioxide; the particle size of the modified silicon dioxide is 5-15nm. In the particle size range, the nano silicon dioxide has very strong hydration activity and Ca (OH) in solution 2 The reaction forms calcium silicate hydrate gel, improves the early strength of concrete, has a large number of pores in the sprayed concrete, particularly has a spatial network structure of ettringite, and the nano silicon dioxide can be well filled in the pores due to the extremely small particle size, so that the compactness of the sprayed concrete is improved, and the mechanical property of the sprayed concrete is improved.
Experiments show that the mother liquor is very stable in an acid system. In order to avoid the delamination, the pH value should be adjusted to be acidic. Only in such cases will the shelf life be extended. The use of dilute sulfuric acid has a great influence on the stability of the accelerator. When the pH value is 2.5, the stability of the accelerating agent is very poor when the accelerating agent is kept still, and the stable period is only 0.5d. Along with the increase of the mixing amount of the dilute sulfuric acid, the stability of the accelerator mother liquor is obviously improved, and when the pH value is smallAt 2.45, the stable period of the accelerator is kept above 30 days and no demixing and sedimentation phenomena occur. Hydrolysis of polyaluminium sulfate in solution produces Al (OH) 3 Precipitation with H + Addition of dilute sulfuric acid introduces a portion of H + The pH value of the accelerator is lowered, and hydrolysis of aluminum ions is inhibited, so that the stability of the accelerator is improved.
As a preferable technical scheme of the invention, the accelerator also comprises a defoaming agent and a dispersing agent, wherein the defoaming agent accounts for 0.2-1.5% of the total weight of the accelerator; 2-6% of dispersant;
the dispersant is specifically QM-168C dispersant; the accelerator doped with the QM-168C dispersant has better stability than the accelerator added with polyacrylamide, and the stabilization period can reach 60 days at most.
A method for preparing an alkali-free and fluorine-free accelerator, comprising the following steps:
step 1: heating water to 40-65 ℃, firstly adding 1/3-2/3 of polyaluminium sulfate, continuously stirring at the rotating speed of 100-200r/min for 3-8min, continuously adding the rest polyaluminium sulfate, and stirring for dissolving;
step 2: keeping the temperature, stirring, and dripping diethanolamine for performing a complex reaction for 8-15min;
and 3, step 3: keeping the temperature, stirring, and dripping ethylene glycol to perform a complex reaction for 8-15min;
and 4, step 4: keeping the temperature, adding the rest compound components while stirring, stirring for 8-15min, stopping stirring, standing the solution, and naturally cooling the solution to room temperature to obtain the accelerator.
Under the condition of constant mixing proportion, the change of synthesis environment has great influence on the performance of the novel alkali-free fluorine-free liquid setting accelerator, and the length of stirring time, the synthesis temperature and the speed of stirring all have influence on the performance of the liquid setting accelerator. Through a single-factor controlled variable test, the stirring can generate bubbles in the solution when the stirring speed exceeds 200r/min, and the existence of the bubbles can reduce the nucleation barrier of the supersaturated aluminum sulfate solution, so that crystallization is realized, the stability is influenced, and the coagulation time is also influenced. After the bubbles are cooled, the bubbles are agglomerated, and the stability is seriously influenced. Therefore, the rotation speed range in the step 1 is 140-160r/min as a preferable scheme of the invention.
By studying the reaction temperature, it was found that: the influence of the synthesis temperature on the stability is that the higher the temperature is, the higher the solubility of the aluminum sulfate is, and the supersaturated solution is favorably formed; on the other hand, the higher the reaction temperature, the more favorable the hydrolysis of aluminum ions, and the system becomes colloidal. At a lower temperature, the system reacts to form a thick high saturated solution, and crystallization instability is dominant; at higher temperature, the ionization degree of water is increased along with the increase of temperature, and more OH is released in the water - The system reacts to form milky colloidal liquid Al 3+ Hydrolytic coagulation, delamination instability, predominates, as evidenced by a decrease in initial pH with increasing temperature.
As a preferred embodiment of the present invention, the temperature during the reaction is in the range of 50 to 58 ℃.
The holding time also affects the change of the state of the system from polymeric aluminum sulfate dissolution to A1 3+ Hydrolysis requires a certain time course. Tests show that the dissolution of aluminum sulfate can be ensured by shorter heat preservation time, aluminum ions are less hydrolyzed, and a system reacts to form a thick high-saturation solution, so that crystallization instability is dominant; when the holding time is prolonged, enough OH is generated due to the ionization of water - 、A1(OH) 3 Continuously polymerizing into large particles, forming milky colloidal liquid in the system, and generating coagulation and delamination after the particles grow to a certain degree. When the heat preservation time is longer than 2h, the sample is changed into milky colloidal liquid from a semitransparent state, and the difference of the stabilization periods of the sample is large. Under different heat preservation times, the initial setting time is not greatly different, and the final setting time is greatly different; when the heat preservation time is 1.5h, the final setting time is shortest and is only 8min31s; when the temperature is kept for 3 hours, the final setting time is the longest, namely 9min57s, and the setting time of each group of samples with the doping amount of 8 percent can meet the requirement of GB/T30159-2017. Comprehensive stability, condensation time and production efficiency, and the heat preservation time is controlled to be more suitable between 1.5 and 2 hours.
The solubility of aluminium sulphate or polyaluminium sulphate is closely related to temperature and gradually increases with increasing temperature. In order to improve the action effect of the liquid accelerator, the accelerator solution should be ensured to have a proper proportion of accelerating components, so that the selection of a reasonable synthesis temperature is important during synthesis. Secondly, when the accelerator is synthesized, the accelerating components need to be fully dissolved, and in the reaction process of the whole system, various materials need to interact to generate chemical reaction to generate stable chemical products, particularly the interaction between the accelerating components and the complexing agent and the stabilizing agent, so that when the liquid accelerator is synthesized, how to ensure that all the components fully react with high quality needs to set proper heat preservation time. As a preferred scheme of the invention, the overall heat preservation time is 1.5-2h in the preparation process.
By researching the preparation technology of the novel alkali-free fluorine-free liquid accelerator and the adaptability of the alkali-free accelerator and cement, basic data are provided for the application technology of the novel alkali-free accelerator in concrete, and finally, a matched process system of the novel alkali-free accelerator is formed; the achievement can be used for various tunnel primary support constructions, can be used for solving the problems of poor adaptability to cement, large rebound quantity of sprayed concrete, large dust quantity generated in the construction process, easy generation of alkali-aggregate reaction, difficult construction and the like, and can ensure the construction quality of tunnel primary support engineering; secondly, with the continuous improvement of wet spraying equipment, the spraying process is continuously innovated, the alkali-free wet spraying construction process is mature day by day, and the engineering benefit brought by the alkali-free wet spraying construction process is gradually remarkable. The alkali-free wet spraying has wide application prospect not only in railway tunnels, including water conservancy and hydropower and underground engineering protection. The technology has the advantages of economic use price, 16 percent lower than that of the traditional liquid accelerator, higher cost performance, capability of greatly reducing the engineering construction cost and higher popularization value.
In summary, due to the adoption of the technical scheme, the invention has the beneficial effects that:
1. the invention provides an alkali-free and fluorine-free liquid accelerator, which comprises the following components in an optimal mixing ratio: 53-57% of polyaluminium sulfate, 4-6% of diethanolamine, 1-2% of ethylene glycol, 2-3% of magnesium sulfate, 3-4% of modified silicon dioxide, 1% of defoaming agent, 5% of dispersing agent and the balance of water, so that the prepared quick-setting agent has good performance and good stability, the initial setting time is 3min and 20s, the final setting time is 4min and 9s, the 6h strength can reach 1.3MPa, the 1d strength is 13MPa, the 28d compressive strength ratio is more than 100%, the 90d strength retention rate is more than 100%, and the stability is good.
2. After the alkali-free liquid accelerator obtained by the preparation process is doped, a large amount of AFt is generated in cement slurry through hydration to form a space network structure, and AFt micro-expansion enables hardened slurry to be more compact, so that the early strength of the cement slurry is improved. A large amount of AFt in the slurry is converted into AFm along with the prolonging of the maintenance time, the structure is more compact, and the later-stage compressive strength of the cement slurry is effectively guaranteed.
3. In the compound composition, the alcohol amine and the glycol have excellent complexing effect and can complex a large amount of metal ions (Al) 3+ ) Form stable complexes with Al and can increase Al 3+ So that it is stably present in the solution.
4. The accelerator disclosed by the invention does not contain alkaline substances or fluoride ions in the formula, has low pH value, is less in human skin erosion, high in early strength, free of loss of later strength, good in stability and adaptability, and belongs to an economic and environment-friendly pollution-free green product.
5. The alkali-free and fluorine-free liquid accelerator can meet the requirement of qualified products when the mixing amount is 8 percent. The alkali-free fluorine-free liquid accelerator has good adaptability with different types of cement, and the proper mixing amount of the accelerator needs to be determined by tests in advance for different types of cement. The alkali-free fluoride-free liquid accelerator has good compatibility with different water reducing agents, and the effect of the accelerator is more obvious when the water reducing agent is added. The alkali-free fluorine-free liquid accelerator has good adaptability to different admixtures, namely fly ash and S95-grade mineral powder.
6. The modified silicon dioxide as the early strength agent can obviously improve the problem of low early strength of the accelerator in the use process, has better effect on improving the early strength of the accelerator in the use process when the mixing amount is 3 percent, can improve the compressive strength by more than 300 percent in1 day and can improve the strength by more than 15 percent in 28 days.
Detailed Description
The present invention will be described in detail below.
In order to make the objects, technical solutions and advantages of the present invention more clearly understood, the following examples further illustrate the present invention in detail. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
The polyaluminium sulfate, diethanolamine, ethylene glycol, magnesium sulfate, nanosilica, all of which are mentioned in the following examples of the present invention, are commercially available.
Modification of nano silicon dioxide: the method comprises the steps of modifying the nano-silica by using a silane coupling agent as a matrix, adding a certain amount of dilute sulfuric acid to promote the hydroxyl in the silane coupling agent to generate a polymerization reaction with the silica, increasing the grafting rate of the silane coupling agent, and placing the reacted solution in an ultrasonic dispersion instrument to improve the agglomeration of the nano-silica to obtain the stable modified silica.
The technical performance index requirements of the liquid alkali-free accelerator are shown in the following table 1:
table 1 shows the technical performance index requirements of the liquid alkali-free setting accelerator
The test method was performed according to the test standard.
Example 1
This example 1 provides 6 preferred sets of liquid accelerator formulation compositions, 100% total composition, balance water, as shown in table 2:
TABLE 2 compounding ratio of each accelerator
Testing the technical performance index requirement of the accelerator on the 6 groups of compositions, wherein the test object is the reference cement, and the mixing amount is 7%; the test results are shown in table 3 below:
TABLE 3 summary of Performance tests
Example 2
This example is a study of the optimization of conditions in the preparation of accelerator formulations
The key point of the preparation and synthesis of the liquid accelerator is to solve the problem of the solubility of the accelerating component of the accelerator, particularly the liquid accelerator taking an aluminum-based compound as the accelerating component. Because the solubility of the aluminum sulfate is lower at normal temperature, the aim of controlling the synthesis process is to promote the dissolution of the aluminum sulfate and maintain the content of aluminum ions in the solution for a long time, thereby playing the effect of the accelerator and meeting the technical requirements of setting time and early strength. Therefore, the selection of a proper synthesis process is a basic prerequisite for preparing a qualified liquid accelerator.
Research on reaction conditions shows that the performance of the compound product is not only the proportion of each component, but also the cooperative matching of each parameter in the preparation process is indispensable; through research on synthesis conditions, changes in stirring speed and reaction temperature have a great influence on the stability of the accelerator. A study of the preparation was carried out with the formulations of examples 1 to 5.
Influence of stirring speed on setting time of cement paste
The constant reaction temperature T =55 ℃ and the holding time T =1h, the stirring speed of the synthesis reaction was varied, and the coagulation time of the synthesized product was tested to evaluate the influence of the stirring speed on the stability and coagulation time of the product, and the test results are shown in table 4.
TABLE 4 influence of stirring speed on the Performance of alkali-free and fluorine-free liquid accelerators
Tests show that when the mixing ratio is fixed, when the stirring speed exceeds 200r/min, the solution can generate bubbles by stirring, and the bubbles are agglomerated after cooling, so that the stability is seriously influenced. The data in the table show that the prepared accelerator has short stabilization period which can only stabilize 23 days at most, and the setting time under low-speed stirring (< 200 r/min) can meet the requirement of GB/T30159-2017 from the setting time; while the initial setting and final setting time under high-speed stirring (more than or equal to 200 r/min) are prolonged. From the viewpoint of comprehensive stability, setting time and production efficiency, the stirring speed is preferably controlled to be not more than 160r/min. The influence of the stirring speed on the stability is mainly that the thick liquid bubbles due to high-speed stirring, and the bubbles cannot be eliminated after cooling because the thick liquid has high viscosity. The influence of the bubbles on the system is probably that the existence of the bubbles reduces the nucleation barrier of the supersaturated aluminum sulfate solution, so that crystallization is realized, the stability is influenced, and the coagulation time is also influenced. When the stirring speed is too high, the solution can generate bubbles by stirring, and the bubbles are agglomerated after cooling, so that the stability is seriously influenced.
Influence of the reaction temperature T on the setting time of the cement paste
The holding time T =1h and the stirring speed v =150r/min were selected, the temperature T of the synthesis reaction was changed, the influence of the reaction temperature on the product stability and the setting time was investigated, and the test results are shown in table 5.
TABLE 5 Effect of reaction temperature on setting time of Accelerator
As can be seen from the data, the higher the synthesis reaction temperature, the poorer the stability of the final accelerator product. The test process shows that the early precipitation of the samples synthesized at 45 and 55 ℃ is not obvious, the solution is crystallized along with the prolonging of the time, the slight precipitation appears in the first few days and the later precipitation is obvious for the samples synthesized at 65, 75 and 85 ℃, and the precipitation is totally aggregated along with the prolonging of the time. As for the setting time, the setting time of the samples synthesized at different temperatures can meet GB/T30159-2017. Considering the comprehensive stability and the condensation time, the synthesis temperature is preferably controlled to be about 50-58 ℃. The influence of the synthesis temperature on the stability is that the higher the temperature is, the higher the solubility of the aluminum sulfate is, and the supersaturated solution is favorably formed; on the other hand, the higher the reaction temperature, the more favorable the hydrolysis of aluminum ions, and the system becomes colloidal. At a lower temperature, the system reacts to form a thick high saturated solution, and crystallization instability is dominant; at higher temperature, the ionization degree of water is increased along with the increase of temperature, and more OH is released in the water - The system reacts to form milky colloidal liquid Al 3+ Hydrolytic coagulation, delamination instability, predominates, as evidenced by a decrease in initial pH with increasing temperature.
Through the research and analysis, the key process parameters are determined as follows: the optimal stirring speed is 150r/min, the reaction temperature is 55 ℃, and the heating and heat preservation are carried out for 2h after the reaction is finished.
Example 3
A method for preparing an alkali-free fluorine-free liquid accelerator comprises the following steps:
step 1: heating water to 40 ℃, firstly adding half of polyaluminium sulfate, continuously stirring for 8min at the rotating speed of 140r/min, continuously adding the rest polyaluminium sulfate, and stirring for dissolving;
step 2: keeping the temperature and the rotating speed unchanged, and dropwise adding diethanolamine to perform a complex reaction for 12min;
and step 3: keeping the temperature and the rotating speed unchanged, and dropwise adding ethylene glycol to perform complexation reaction for 15min;
and 4, step 4: keeping the temperature and the rotating speed unchanged, adding the rest compound components, stirring for 8min, stopping stirring, standing the solution, naturally cooling the solution to room temperature to obtain the accelerator #1, and controlling the total heat preservation time for 2h.
Example 4
A method for preparing an alkali-free fluorine-free liquid accelerator, wherein the formula proportion of the accelerator refers to 1-5, and the method specifically comprises the following steps:
step 1: heating water to 50 ℃, firstly adding half of polyaluminium sulfate, continuously stirring for 8min at the rotating speed of 160r/min, continuously adding the rest polyaluminium sulfate, and stirring for dissolving;
and 2, step: keeping the temperature and the rotating speed unchanged, and dropwise adding diethanolamine to perform a complex reaction for 12min;
and step 3: keeping the temperature and the rotating speed unchanged, and dropwise adding ethylene glycol to perform complexation reaction for 15min;
and 4, step 4: keeping the temperature and the rotating speed unchanged, adding the rest compound components, stirring for 8min, stopping stirring, standing the solution, naturally cooling the solution to room temperature to obtain the accelerator #2, and controlling the total heat preservation time for 2h.
Example 5
A method for preparing an alkali-free fluorine-free liquid accelerator comprises the following steps:
step 1: heating water to 60 ℃, firstly adding half of polyaluminium sulfate, continuously stirring for 8min at the rotating speed of 150r/min, continuously adding the rest polyaluminium sulfate, and stirring for dissolving;
step 2: keeping the temperature and the rotating speed unchanged, and dropwise adding diethanolamine to perform a complex reaction for 12min;
and step 3: keeping the temperature and the rotating speed unchanged, and dropwise adding ethylene glycol to perform complexation reaction for 15min;
and 4, step 4: keeping the temperature and the rotating speed unchanged, adding the rest compound components, stirring for 8min, stopping stirring, standing the solution, naturally cooling the solution to room temperature to obtain the accelerator #3, and controlling the total heat preservation time for 2h.
Testing the technical performance index requirements of the accelerators of the #1, #2 and #3, wherein the test object is reference cement, and the doping amount is 7 percent; the test results are shown in table 6 below:
table 6 is a summary table of the properties of the three accelerators
Experiments on the three accelerators obtained by the optimal reaction conditions and the optimal proportion on the basis of the standard cement show that the initial setting time is kept within 3 minutes and half, the final setting time is not more than 5 minutes, the compressive strength of 1 day is more than 13.5MPa, and the compressive strength of 28 days is more than 100%. Has good performance.
The raw materials used in the production of cement by cement plants in different places are different, and the control of each specific value of the cement clinker by each cement plant is also different, so that the chemical composition difference of the clinker is larger. In addition, the admixture has a large variety and different mixing amounts, so that the compatibility of the accelerator with different types of cement may be caused.
The suitability of different cements with accelerator #2 prepared in example 4 is tested as shown in the table below:
selecting standard cement, conch cement, jidong cement and kui cement, wherein the mixing amount of the accelerator is 7%,8% and 9% respectively; the test properties are shown in Table 7:
table 7 shows the performance test of the setting accelerator in different cements
As can be seen from the above table, the novel alkali-free accelerator can achieve the accelerating effect on different types of cement, and is completely consistent with the relevant regulations of accelerator for sprayed concrete. When the mixing amount of the novel alkali-free liquid accelerator is gradually increased, the setting time of four kinds of cement is gradually reduced. In comparison, the novel alkali-free liquid accelerator has the best accelerating effect on the golden corner cement among the four cements, and the setting time of the golden corner cement is greatly shortened along with the increase of the accelerator. In all groups, the longest setting time is the reference cement, when the mixing amount of the accelerator is 7%, the initial setting time is measured to be 5min18s, the final setting time is measured to be 8min12s, and the requirements of national standard and iron standard on the setting time of the clean slurry cannot be met. The alkali-free accelerator can form a large amount of ettringite hydration products, reduce C/S of C-S-H to a certain extent and reduce the pH value of cement slurry, so that the alkali-free accelerator has different effects on the hydration influence and strength development of cement when being used for different cements.
Through studying the influence of different mixing amount of the novel alkali-free liquid accelerator on the early compressive strength and the later compressive strength ratio of different types of cement, the test performance is shown in table 8, the adaptability of the novel alkali-free liquid accelerator and the cement is further studied, and then the suitable mixing amount of the accelerator in different types of cement is determined:
TABLE 8 is a summary of the compressive strengths at different times
In conclusion, the novel alkali-free liquid accelerator has good compatibility with different types of cement. The optimal mixing amount of different cements is different, the optimal mixing amount of the reference cement, the conch cement and the golden corner cement is 8%, the optimal mixing amount of the Jidong cement is 7%, and at the moment, the novel alkali-free liquid accelerator can effectively promote the cement coagulation and can also obviously improve the early strength and the later strength of the mortar.
Adaptability test of novel liquid accelerator #2 and different mineral admixtures
The admixture is used as an indispensable functional component in the existing concrete, has an important effect on adjusting and improving the performance of the concrete, and is very widely applied. Meanwhile, the blending of the admixture in a certain proportion is also beneficial to realizing the resource utilization of solid waste, and the cost is reduced while the environmental protection problem is solved. Accelerator accelerating agent C 3 A and C 3 And S hydration, namely, the cement is doped with the mixed material, so that the clinker content in the cement is substantially reduced, and clinker minerals participating in early hydration in the cement are reduced, so that the cement coagulation is delayed.
Table 9 is a summary table of the adaptability results of the setting accelerator to different mineral admixtures
It can be seen that the amount of admixture should not be too high in the design of the mix proportion of the shotcrete. This is because the mineral admixture retards the hydration of the cement, and the addition of the accelerator, which promotes the hydration, is calciumniteThe formation of stone provides a large amount of Al 3+ And SO 4 2- Ion, but the active ingredient in the admixture is low, and the reaction is carried out for a period of time before the reaction with Al provided by the accelerating agent 3+ And SO 4 2- The ions are normally hydrated to generate ettringite crystals.
To summarize:
the alkali-free and fluorine-free liquid accelerator can meet the requirement of qualified products when the mixing amount is 8 percent. The alkali-free fluorine-free liquid accelerator has good adaptability to different types of cement, and the proper mixing amount of the accelerator needs to be determined by tests in advance for different types of cement. The alkali-free fluorine-free liquid accelerator has good compatibility with a polycarboxylic acid water reducing agent, and the effect of the accelerator is more obvious when 1% of water reducing agent is added. The alkali-free fluorine-free liquid accelerator has good adaptability to different admixtures, namely fly ash and S95-grade mineral powder.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.
Claims (4)
1. The liquid accelerator is characterized by comprising the following components in percentage by mass:
50-60% of polyaluminium sulfate, 4-8% of diethanolamine, 1-5% of magnesium sulfate, 1-4% of ethylene glycol, 2-5% of modified silicon dioxide and the balance of water to 100%;
the ratio of the diethanol amine to the ethylene glycol is (4-8): 1;
the modified silicon dioxide is obtained by modifying according to the following specific mode: modifying nano-silica by using a silane coupling agent as a matrix, adding dilute sulfuric acid to promote hydroxyl in the silane coupling agent to generate a polymerization reaction with the silica, and placing the reacted solution in an ultrasonic dispersion instrument for 3-5min to obtain the modified nano-silica; the particle size of the modified silicon dioxide is 5-15nm;
in the preparation process of the liquid accelerator, the stirring speed is controlled to be 140-160r/min, and the synthesis temperature is controlled to be 50-58 ℃.
2. The liquid accelerator according to claim 1, wherein the liquid accelerator comprises the following components in percentage by mass: 53-57% of polyaluminium sulfate; 4-6% of diethanolamine; 2-3% of magnesium sulfate; 1-2% of ethylene glycol; 2-4% of modified silicon dioxide, and the balance of water to 100%.
3. The liquid accelerator according to claim 1, wherein the accelerator further comprises 0.2-1.5% of a defoaming agent, 2-6% of a dispersing agent; the defoamer is an organic silicon defoamer; the dispersant is a QM-168C dispersant.
4. A method for producing the liquid accelerator according to claim 3, comprising the steps of:
step 1: preparing polyaluminium sulfate, diethanolamine, magnesium sulfate, ethylene glycol, modified silicon dioxide, a defoaming agent and a dispersing agent according to a proportion, heating water to 40-65 ℃, firstly adding 1/3 to 2/3 of the polyaluminium sulfate, continuously stirring at a rotating speed of 100-200r/min for 3-8min, continuously adding the rest polyaluminium sulfate, and stirring and dissolving;
and 2, step: keeping the temperature, stirring, and dropwise adding diethanolamine to perform a complex reaction for 8-15min;
and step 3: keeping the temperature, stirring, and dripping ethylene glycol to perform a complex reaction for 8-15min;
and 4, step 4: preserving heat, stirring and adding the rest compound components; and after stirring for 8-15min, stopping stirring, standing the solution, and naturally cooling the solution to room temperature to obtain the accelerating agent.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202111628630.XA CN114276042B (en) | 2021-12-28 | 2021-12-28 | Alkali-free fluorine-free liquid accelerator and preparation method thereof |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202111628630.XA CN114276042B (en) | 2021-12-28 | 2021-12-28 | Alkali-free fluorine-free liquid accelerator and preparation method thereof |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN114276042A CN114276042A (en) | 2022-04-05 |
| CN114276042B true CN114276042B (en) | 2023-03-24 |
Family
ID=80877590
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202111628630.XA Active CN114276042B (en) | 2021-12-28 | 2021-12-28 | Alkali-free fluorine-free liquid accelerator and preparation method thereof |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN114276042B (en) |
Families Citing this family (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114853440A (en) * | 2022-04-24 | 2022-08-05 | 山东润凝新材料科技有限公司 | HN-S material, preparation method thereof and pavement patching material |
| CN114804694B (en) * | 2022-05-09 | 2022-11-11 | 北京市政路桥管理养护集团有限公司 | Liquid accelerator for tunnel concrete and preparation method thereof |
| CN115259723B (en) * | 2022-06-16 | 2023-10-20 | 武汉源锦建材科技有限公司 | High-durability alkali-free accelerator for foundation pit reinforcement and preparation method thereof |
| CN116477873B (en) * | 2023-03-10 | 2023-12-05 | 铁科腾跃科技有限公司 | Early-strength fluorine-free chlorine-free alkali-free liquid accelerator and preparation method thereof |
| CN116354642A (en) * | 2023-03-27 | 2023-06-30 | 广东长大道路养护有限公司 | Environment-friendly liquid accelerator and preparation method thereof |
| CN116693229B (en) * | 2023-05-30 | 2024-05-14 | 中铁四局集团有限公司 | Preparation method of alkali-free fluorine-free liquid accelerator |
| CN117682788A (en) * | 2023-12-14 | 2024-03-12 | 四川嘉兆丰新材料科技有限公司 | Fluorine-free alkali-free rare earth-based modified amine liquid accelerator and preparation method thereof |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE2011150A1 (en) * | 1970-03-10 | 1971-09-30 | Ludwig Horlmg Fabrik chemischer Baustoffe GmbH, 3283 Lugde | Organic additives for the rapid setting of concrete |
| CN103553406B (en) * | 2013-09-27 | 2016-08-17 | 中国建筑材料科学研究总院 | A kind of alkali-free chlorine-free liquid accelerator based on industrial polymerisation aluminum sulfate and preparation method thereof |
| CN108358497A (en) * | 2018-05-10 | 2018-08-03 | 江苏地基工程有限公司 | Novel foundation pit waterproof curtain added material alkali-free liquid accelerator and preparation method thereof |
| CN112723787A (en) * | 2020-12-30 | 2021-04-30 | 山西佳维新材料股份有限公司 | Fluorine-free liquid accelerator and preparation method and application thereof |
-
2021
- 2021-12-28 CN CN202111628630.XA patent/CN114276042B/en active Active
Also Published As
| Publication number | Publication date |
|---|---|
| CN114276042A (en) | 2022-04-05 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN114276042B (en) | Alkali-free fluorine-free liquid accelerator and preparation method thereof | |
| CN109574538B (en) | Concrete glue reducing agent and preparation process and application method thereof | |
| CN111333362A (en) | Low-dosage high-early-strength alkali-free liquid accelerator and preparation method thereof | |
| CN110734242B (en) | Sprayed concrete alkali-free liquid accelerator for alpine regions and preparation method thereof | |
| CN112358224B (en) | Concrete glue reducing agent and preparation method and application thereof | |
| CN111116081B (en) | Graphene modified concrete retarder and preparation method thereof | |
| CN111960713B (en) | High-performance alkali-free liquid accelerator and preparation method thereof | |
| CN109790261B (en) | Preparation method of block slow-release concrete admixture | |
| CN110818310A (en) | Concrete glue reducing agent and preparation method and application thereof | |
| CN118290062B (en) | Nano hydrated calcium carbonate aluminate early strength agent and preparation method thereof | |
| CN110963732A (en) | Environment-friendly alkali-free liquid accelerator and normal-temperature preparation method thereof | |
| CN109111145B (en) | High-stability low-alkali liquid accelerator and preparation method thereof | |
| CN109485291A (en) | A kind of early diminishing complexing agent and preparation method thereof by force of novel poly-carboxylic high-performance nanometer seed crystal | |
| WO2024093786A1 (en) | Method for preparing early-strength liquid accelerator free of alkali, chlorine, and fluorine | |
| CN111847967A (en) | Machine-made sand regulator for concrete, concrete and preparation method thereof | |
| CN113003976A (en) | Alkali-free liquid accelerator containing fluorosilicate and preparation method and application thereof | |
| CN113429149A (en) | High early strength alkali-free liquid accelerator and preparation method thereof | |
| CN115286275A (en) | Retarding and water resisting agent suitable for magnesium phosphate cement system | |
| CN112225486B (en) | Stable alkali-free liquid accelerator and preparation method and application thereof | |
| CN113582573A (en) | Accelerating agent and preparation method and application thereof | |
| CN113264703A (en) | High-performance concrete glue reducing agent and preparation method thereof | |
| CN110510912B (en) | Wet-mixed mortar additive and preparation method thereof | |
| CN115259709B (en) | Modified glass bead and preparation method thereof, coagulation-accelerating early strength agent and preparation method thereof | |
| CN114988744B (en) | Concrete shrinkage-reducing reinforcing agent and application thereof | |
| CN115403294A (en) | High-stability alkali-free chlorine-free fluorine-free liquid accelerator and preparation method thereof |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| GR01 | Patent grant | ||
| GR01 | Patent grant |